The present invention relates to the field of metal coating, more specifically to a coating containing coating encapsulated microspheres which improve the corrosion resistance of an article by dispensing the encapsulated coating when the article is injured.
A persistent problem is to provide metal articles which are resistant to corrosion that inherently attacks such articles in normal usage. With some metal articles, the need to provide the maximum degree of corrosion resistance is particularly great, in view of the corrosive environments in which they are utilized. For example, vehicle components are typically exposed to corrosive salts and other corrosive agents which would cause rapid deterioration, both functionally and aesthetically. Numerous other articles made of metals must be protected or corrosion will eventually occur.
It is well known that the corrosion resistance of metal articles can be improved by applying coatings, either in single or multiple layers. Such layers provide greater inherent resistance to attack by corrosive agents. For example, it is known that improvements in the corrosion resistance of a metal substrate can be achieved by applying coatings such as electroplating, paints, dyes, and chromate films.
However, such coatings can be damaged during normal wear. This is particularly a concern in metal parts which flex during use such as suspension components, coil springs, actuators, etc. The coating is prone to crack at the flexed areas. When the coating becomes damaged or cracks, a path in a localized area of the article is opened to the metal substrate. The corrosive agents can then directly attack the metal substrate and the article rapidly deteriorates in the localized area. Typically, damage in the localized area requires the repair or replacement of the entire article.
It is therefore desirable to provide an anti-corrosion coating that is self-healing and blocks a path opened to the metal substrate.
The coated article according to the present invention includes a coating having coating encapsulated micro-spheres which maintain the coating in a fluid state until the micro-spheres are ruptured.
The substrate is preferably a vehicle component such as a spring or suspension component which is typically subjected to flexing and operates in a high corrosion environment. However, the type of substrate, or the form in which it is provided for treatment in accordance with the invention, is not limited to any particular part.
The coating is preferably an anti-corrosion coating such as a paint or undercoating which contains a quantity of coating encapsulated micro-spheres. The coating encapsulated micro-spheres are manufactured to encapsulate a coating material in a fluid state. The coating encapsulated micro-spheres are retained in the coating to form a matrix of hardened coating and coating encapsulated micro-spheres which maintain the coating material in the fluid state. By incorporating a mix of different coating encapsulated micro-spheres which encapsulate different fluid coatings, a multiple of properties can be incorporated directly into the coating. The coating may therefore be tailored to provide desired anti-corrosion properties.
With the present invention, damage to the coating which causes a fissure in the coating also breaks open the coating encapsulated micro-spheres adjacent the crack or fissure. The broken coating encapsulated micro-spheres release the fluid coating material contained therein. Because the coating encapsulated micro-spheres release the encapsulated coating material in the fluid state the coating material flows into the fissure to coat the exposed substrate. This provides a xe2x80x9cself-healingxe2x80x9d ability to the coating which protects the substrate even after the coating is damaged.